staging: stradis: fix error handling and information leak to userland

configure_saa7146() didn't free irq on error.
saa_open() didn't decrease reference count of saa on error.
saa_ioctl() leaked information from the kernel stack to userland as it
didn't fill copied structs with zeros.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>